Abstract
A paper machine clothing has a substrate with an upper side, a lower side, two lateral edges and a usable region between the two lateral edges. The usable region is formed with a plurality of through-channels extending through the substrate and connecting the upper side with the lower side. The through-channels are non-cylindrical with a cross sectional area becoming smaller when going in a thickness direction of the substrate from the upper side to a middle region of the substrate between the upper side and the lower side, wherein a shape of the cross sectional area of at least one through-channel, preferably of all through-channels, of the plurality of through-channels changes proceeding in the thickness direction of the substrate from the upper side to the lower side.
Claims
1. A paper machine clothing, comprising: a substrate having an upper side, a lower side, two lateral edges, and a usable region between said two lateral edges; said usable region having a plurality of through-channels formed therein extending through said substrate and connecting said upper side with said lower side; said through-channels being non-cylindrical, with a cross sectional area becoming smaller in a thickness direction of said substrate from said upper side to a middle region of said substrate between said upper side and said lower side; and a shape of the cross sectional area of at least one of said through-channels changing in the thickness direction of the substrate proceeding from said upper side to said lower side.
2. The paper machine clothing according to claim 1, wherein the shape of all of said through-channels of the plurality of through-channels changes in the thickness direction from said upper side to said lower side.
3. The paper machine clothing according to claim 1, wherein the shape of the cross sectional area is substantially more elliptical in an upper region of said through-channel than in a lower region of said through-channel.
4. The paper machine clothing according to claim 1, wherein the shape of the cross sectional area in the upper region of said through-channel has a first dimension extending in cross-machine direction and a second dimension extending in machine direction, and wherein the first dimension is smaller than the second dimension.
5. The paper machine clothing according to claim 1, wherein the shape of the cross sectional area in the upper region of said through-channel has a first dimension extending in cross-machine direction and a second dimension extending in machine direction, and wherein the first dimension is larger than the second dimension.
6. The paper machine clothing according to claim 1, wherein the shape of the cross sectional area at said lower side of said substrate is substantially circular.
7. The paper machine clothing according to claim 1, wherein an upper rim of at least one of the plurality of said through-channels directly contacts an upper rim of at least one other neighboring through-channel of the plurality of said through-channels.
8. The paper machine clothing according to claim 7, wherein at least 90% of said through-channels in said usable region of said substrate have an upper rim that directly contacts an upper rim of at least one other neighboring through-channel of the plurality of through-channels in said usable region of said substrate.
9. The paper machine clothing according claim 8, wherein all of said through-channels in said usable region of said substrate have an upper rim that directly contacts an upper rim of all other neighboring through-channels of the plurality of through-channels in said usable region of said substrate.
10. The paper machine clothing according to claim 1, wherein less than 20% of a surface on said upper side of said substrate is flat and substantially orthogonal to the thickness direction of said substrate.
11. The paper machine clothing according to claim 10, wherein less than 5% of the surface on said upper side of said substrate is flat and substantially orthogonal to the thickness direction of said substrate.
12. The paper machine clothing according to claim 1, wherein between 70% and 90% of a surface on said lower side of said substrate is flat and substantially orthogonal to the thickness direction of said substrate.
13. The paper machine clothing according to claim 12, wherein approximately 80% of the surface on said lower side of said substrate is flat and substantially orthogonal to the thickness direction of said substrate.
14. The paper machine clothing according to claim 1, wherein the cross sectional area of said through-channels in said usable region of said substrate continuously decreases proceeding in the thickness direction of said substrate from said upper side to said lower side of said substrate.
15. The paper machine clothing according to claim 1, wherein the cross sectional area of said through-channels in said usable region of said substrate continuously decreases in the thickness direction of said substrate from said upper side to the middle region of said substrate, and increases again in the thickness direction of said substrate from the middle region of said substrate to said lower side of the substrate.
16. The paper machine clothing according to claim 1, wherein at least 90% of said through-channels in said usable region of said substrate are arranged in a non-checkered pattern.
17. A method of producing the paper machine clothing according to claim 1, the method comprising the following steps: providing a substrate having a first surface and a second surface; and forming a plurality of non-cylindrical through holes into a usable region of the substrate with a laser and cooling the substrate during the step of forming the through holes.
18. The method according to claim 17, wherein the step of cooling the substrate comprises blowing cold air onto the substrate during the step of forming the through holes with the laser.
19. The method according to claim 17, wherein at least some of the plurality of through holes that are neighboring each other are formed at such a close distance that the neighboring through holes partially overlap each other.
20. The method according to claim 17, which comprises forming the through holes such that, when all of the through holes have been formed into the usable region of the substrate, at least one of the first surface or the second surface in the usable region has disappeared by at least 90%.
Description
(1) In the following, the invention will be explained with respect to some schematic drawings that are not true to scale, wherein:
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING
(2) FIG. 1 shows a method of laser drilling perforation of a substrate according to the prior art;
(3) FIG. 2 shows a substrate place under tension between two rollers according to the prior art;
(4) FIG. 3a shows a cylindrical through section according to the prior art;
(5) FIG. 3b shows a conical through section according to the prior art;
(6) FIG. 3c shows a hyperboloid through section according to the prior art;
(7) FIG. 4 shows a section of a substrate comprising a single through hole of a first type not forming part of the present invention;
(8) FIG. 4a shows an enlarged view of the through hole in FIG. 4 not forming part of the present invention;
(9) FIG. 5 shows a section of a substrate comprising a single through hole of a second type according to the present invention;
(10) FIG. 5a shows an enlarged view of the through hole in FIG. 5 according to the present invention;
(11) FIG. 6 shows a sectional view along lines A-A and B-B in FIG. 4 and along line C-C in FIG. 5;
(12) FIG. 7 shows a sectional view along line D-D in FIG. 5;
(13) FIG. 8 shows a section of a substrate comprising a plurality of through holes of the first type not forming part of the present invention;
(14) FIG. 9 shows a section of a substrate comprising a plurality through holes of the second type according to the present invention;
(15) FIG. 10 shows a sectional view along lines E-E and F-F in FIG. 8 and along line G-G in FIG. 9;
(16) FIG. 11 shows a sectional view along line H-H in FIG. 9;
(17) FIG. 12 shows a sectional view similar to the sectional view of FIG. 10, but with a third type of through holes;
(18) FIG. 13 shows a section of a substrate similar to the one shown in FIG. 8 not forming part of the present invention, but with the through holes are arranged in a non-checkered pattern; and
(19) FIG. 14 shows a section of a substrate similar to the one shown in FIG. 9 according to the present invention, but with the through holes are arranged in a non-checkered pattern.
DETAILED DESCRIPTION OF THE INVENTION
(20) FIG. 4 shows a section of a substrate 20 which section is indicated by a dashed square. The substrate 20 comprises a first surface 22 and an opposite second surface 24 (see FIG. 6), wherein the first surface 22 and the second surface 24 are substantially planar and parallel to each other.
(21) A single through hole 31 of a first type not forming part of the present invention is provided in the center of the section of the substrate 20. FIG. 6 shows a cross sectional view which is taken through the through hole 31 along line A-A or line B-B of FIG. 4. As can be seen from FIGS. 4 and 6, the through hole 31 extends through the substrate 20 in its thickness direction TD along a central axis CA of the through hole 31, the central axis CA being indicated by a dashed line in FIG. 6. Thus, the through hole 31 connects the first surface 22 with the second surface 24 of the substrate 20. The through hole 31 is substantially funnel shaped with a cross sectional area becoming continuously smaller when going in the thickness direction TD from the first surface 22 to the second surface 24. The cross sectional area of a through hole 31 is obtained by cutting the through hole 31 with a plane that is oriented perpendicular to the thickness direction TD of the substrate 20. In this embodiment that does not belong to the present invention the shape of the cross sectional area of the through hole 31 is always circular, no matter at which height level of the substrate the cross sectional area is taken.
(22) The through hole 31 has a circular upper rim 34 where a side wall of the through hole 31 ends and the flat first surface 22 begins. The circular upper rim 34 has a diameter A, as shown in FIG. 4a. Furthermore, the through hole 31 has a circular lower rim 36 where the side wall of the through hole 31 ends and the flat second surface 24 begins. The circular lower rim 36 has a diameter a, as also shown in FIG. 4a. Diameter A of the upper rim is larger than diameter a of the lower rim.
(23) FIG. 5 shows another section of a substrate 20 which section is also indicated by a dashed square. The substrate 20 comprises a first surface 22 and a second surface 24 (see FIG. 7), wherein the first surface 22 and the second surface 24 are substantially planar and parallel to each other.
(24) A single through hole 32 of a second type according to the present invention is provided in the center of the section of the substrate 20. FIG. 6 shows a cross sectional view which is taken through the through hole 32 along line C-C of FIG. 5 and FIG. 7 shows a cross sectional view which is taken through the through hole 32 along line D-D of FIG. 5. As can be seen from FIGS. 5, 6 and 7, the through hole 32 extends through the substrate 20 in its thickness direction TD along a central axis CA of the through hole 32, the central axis CA being indicated by a dashed line in FIGS. 6 and 7. Thus, the through hole 32 connects the first surface 22 with the second surface 24 of the substrate 20. The through hole 32 is substantially funnel shaped with a cross sectional area becoming continuously smaller when going in a thickness direction TD from the first surface 22 to the second surface 24. The cross sectional area of the through hole 32 is obtained by cutting the through hole 32 with a plane that is oriented perpendicular to the thickness direction TD of the substrate 20. In this embodiment the shape of the cross sectional area of the through hole 32 is not constant, what is according to the present invention, but changes when going along the thickness direction TD of the through hole 32. In an upper region of the substrate 20, i.e. in a region close to the first surface 22, the through hole 32 is more oval or elliptical, whereas in a lower region of the substrate 20, i.e. in a region close to the second surface 24, the through hole 32 is more or completely circular. The shape of the cross sectional area of the through hole 32 preferably changes continuously along the thickness direction TD of the substrate 20.
(25) Thus, the through hole 32 has an elliptical upper rim 35 where a side wall of the through hole 32 ends and the flat first surface 22 begins. The elliptical upper rim 35 has a first diameter A and a second diameter B measured orthogonally thereto, as indicated in FIG. 5a. Furthermore, the through hole 32 has a circular lower rim 36 where the side wall of the through hole 32 ends and the flat second surface 24 begins. The circular lower rim 36 has a diameter a, as also shown in FIG. 5a. The second diameter B of the upper rim 35 is larger than the first diameter A of the upper rim 35. The first diameter A of the upper rim 35 is larger than the diameter a of the lower rim 36. Preferably, the second diameter B of the upper rim 35 is at least 5%, more preferably at least 10%, even more preferably at least 15% larger than the first diameter A of the upper rim 35.
(26) According to an advantageous embodiment of the present invention, several of such non-cylindrical through holes are arranged in such a close relationship that they partially overlap each other in the substrate. Examples of such arrangements for the through holes 31 of the first type and the through holes 32 of the second type are shown in FIGS. 8 and 9, respectively. To be more precise, nine corresponding through holes 31, 32 arranged in a checkered pattern are shown in these figures. The through holes 31, 32 each have a respective lower rim 36. Furthermore, for the sake of clarity, also the corresponding upper rims 34, 35 of the through holes 31, 32 are shown, even though these upper rims 34, 35 do not exist anymore as such in the final product. Instead, in the final product, i.e. in the finally perforated substrate 20, through-channels 30 are formed having a respective upper rim 38 that is at least partially delimited by the upper rim 38 of a neighboring through-channel 30. As shown in FIGS. 8 and 9, the originally existing flat or planar first surface 22 of the substrate 20 has almost completely disappeared after the perforation of the substrate 20 in the usable region UR thereof. In alternative embodiments it may have completely disappeared. One reason for the complete disappearance of the originally flat first surface 22 of the substrate 20 could be that the distance between the through holes 31, 32 is chosen even smaller than shown in FIGS. 8 and 9 (as will be explained below in view of FIGS. 13 and 14). An additional or alternative reason for the complete disappearance of the originally flat first surface 22 of the substrate 20 could be that the through holes 31, 32 have been laser-drilled and that the material of the substrate 20 that has been evaporated by the energy of the laser at least partially condensates again on the first surface 22, thus forming some kind of hill or ridge thereon. As a consequence, the upper rim 38 of a corresponding through-channel 30 does not necessarily extend within a plane but is rather a closed line that extends three-dimensionally. It should be noted that the upper rim 38 of the through-channel 30 may extend partially below the originally flat first surface 22 of the substrate 20 and/or extend partially above the originally flat first surface 22 of the substrate 20.
(27) FIGS. 10 and 11 represent views similar to the ones shown in FIGS. 6 and 7, respectively, but now with several neighboring through holes 31, 32 that form the through-channels 30 in the substrate 20 of the final product. In FIG. 10 a location (see reference sign 38) of the upper rim 38 of the through-channel 30 of FIG. 8 is shown that represents an absolute minimum of the upper rim 38. In other words, the upper rim 38 has the largest distance to the originally flat first surface 22 of the substrate 20 which surface 22 is indicated by a dotted line in FIG. 10. The surface of the substrate 20 has a saddle point at this location of the upper rim 38.
(28) In FIG. 11 a location (see reference sign 38) of the upper rim 38 of the through-channel 30 of FIG. 9 is shown (according to the section along line H-H of FIG. 9) that represents an absolute minimum of the upper rim 38 of this through-channel 30. In other words, the upper rim 38 has the largest distance to the originally flat first surface 22 of the substrate 20 which surface 22 is also indicated by a dotted line in FIG. 11. The surface of the substrate 20 has a saddle point at this location of the upper rim 38. A section along line G-G of FIG. 9 is represented by the drawing of FIG. 10. At the location of the upper rim 38 shown in this figure, the upper rim only has a local minimum. Thus, the ridges that separate two neighboring through-channels 30 from each other are higher when following the line G-G compared to the ridges when following the line H-H of FIG. 9. Consequently, the substrate has anisotropic properties.
(29) These anisotropic properties can be used in a beneficial way. For example, the substrate that is perforated in a way as shown in FIGS. 9, 10 and 11 is more stress resistant in the direction parallel to line H-H compared to the direction parallel to line G-G. If line H-H substantially represents the machine direction of the final paper machine clothing the relatively high forces in the machine direction can be absorbed by the substrate 20 while at the same time the substrate 20 provides a relatively large open area on its upper side. Alternatively, if line H-H substantially represents the cross machine direction of the final paper machine clothing the nascent paper web in a forming section can adhere better to the substrate 20 since ridges formed in the substrate 20 between neighboring rows of through channels 30 that extend in cross machine direction are higher than those extending in the machine direction. Consequently, the properties of the substrate 20 can be adjusted to the intended use or the requirements of the paper machine clothing.
(30) FIG. 12 shows a sectional view similar to the cross sectional view of FIG. 10, but of a third type of through holes. This third type of through holes differs from the first and second type of through holes 31, 32 in that the cross sectional area of the through hole of the third type and, thus, the cross sectional area of the corresponding through-channel 30 that is created thereof, continuously increase again when going in the thickness direction TD of the substrate 20 from the middle region MR of the substrate 20 between the upper side and the lower side to the lower side of the substrate 20. In an extreme case, neighboring through holes may not only partially overlap each other on the first side 22 of the substrate 20 but also on the second side 24 thereof.
(31) Finally, FIGS. 13 and 14 show a section of a substrate 20 similar to the one shown in FIGS. 8 and 9, respectively, with the difference that the through holes 31, 32 are arranged in a non-checkered pattern. In FIGS. 8 and 9 each through hole 31, 32 has eight neighboring other through holes 31, 32 wherein the distance to four of these eight neighboring through holes 31, 32 is larger than the distance to the remaining four neighboring through holes 31, 32. Small areas of the originally flat first surface 22 of the substrate 20 are still left.
(32) In contrast, in the examples shown in FIGS. 13 and 14, each through hole 31, 32 has six neighboring other through holes 31, 32 wherein the distance to all these neighboring through holes 31, 32 is substantially the same (for example corresponding to the smaller distance of the embodiments shown in FIGS. 8 and 9). These six neighboring through holes 31, 32 are arranged in a honeycomb pattern around a corresponding through hole 31, 32 in the middle thereof. No areas of the originally flat first surface 22 of the substrate 20 are left after the perforation processes. With such an arrangement, the density of through-channels 31 in the final substrate 20 can be increased, as well as the open area on the upper side of the substrate 20.
LIST OF REFERENCE SIGNS
(33) 20′, 20 substrate 22, 22′ first surface 24, 24′ second surface 26′ first lateral edge 28′ second lateral edge 30′, 30 through-channel 31 through hole of first type 32 through hole of second type 34 circular upper rim of through hole 35 elliptical upper rim of through hole 36 circular lower rim of through hole 38 upper rim of through-channel a, b diameter of lower rim A, B diameter of upper rim CA central axis LB laser beam MR middle region R roller TD thickness direction WD width direction
